Guide for disk type magnetic recorder-reproducers



J. H. JAMES Dec. 26, 1950 GUIDE FOR DISK TYPE MAGNETICRECORDER-REPRODUCERS 6 Sheets-Sheet l Filed July l5, 1947 RECORD PLAYdAlNNTOR BY .7611

ATTO NEY Dec. 26, 1950 J. H. JAMES 2,535,495

` GUIDE FOR DISK TYPE MAGNETIC RECORDER-REPRODUCERS me@ July 15, 1947 6Sheets-Sheet 2 NEY Dec. 26, 1950 J. H. JAMES 2,535,495

GUIDE FOR DISK TYPE MAGNETIC RECORDER-REPRODUCERS Filed July 15, 1947 6Sheets-Sheet 3 HOV. A.C

FiGf7 ay L/M ff MM@ ATTORNEY I N V EN TOR.

Dec. 26, 1950 J. H. JAMES 2,535,495

GUIDE FOR DISK TYPE MAGNETIC RECORDER-REPRODUCERS Filed July l5, 194'? 6Sheets-Sheet 4 E RASE 7-40 PLAY RECORD 7- l5 F' 8 M I/ENTOR.

ATTO NEY Dec. 26, 195o J. H. JAMES 2,535,495

GUIDE FOR DSK TYPE MAGNETIC RECORDER-REPRODUCERS v Filed July 15, 1947 6Sheets-Sheet 5 I INVENTOR.

l T I i"g 76 8 .JJ-NAMES we L l $872 WMM affo' A NORA/Ey Dec, 26, 1950J. H. JAMES 2,535,495

GUIDE FOR DISK TYPE MAGNETIC RECORDER-REPRODUCERS 6 Sheets--SheerI 6Filed July 15, 1947 afg. Il.

9.33 IN VEN TOR. 9J@ 9-5@ J.H.JAMES BY WW@ ATTORNEY Patented Dec. 26,1950 GUIDE Foa DISK TYPE MAGNETIC REcoRDEn-Rnrnonuonns John H. James,Cleveland Heights, Qhio, assigner to The Brush Development Company,4Cleveland, Ohio, a corporation of Ohio Application July 15, 1947,Serial No. 761,062

lyClaiin. 1

This invention relates to magnetic record transducing. and particularlyto novel record transducerscapable of simple manipulation.

Among the objects of the invention are novel transducing systems inwhich a transducing operationmay be. accurately and properly initiated..without.` any complicated threading or adjusting operations` The furtherobjects-.of the invention are novel limiting arrangements having. only afew operatingk elements and which accurately terminate the transducing,when; the endA of the recording isreached.

'Iheforegoilng and other. objects of the invention-willl be. bestunderstood from the following description of V'exempliiications thereof,reference being, had" tothe accompanying drawings where- In:

Fig. 14 is a plan View of a magnetic record transducing'system accordingto the invention;

Figs'. 2 and; 3 are sectional views taken along linesZeeZ; and 3,-3,respectively, of the magnetic record transducing system of Fig. l;

liigs.v 4y and4A are detail sectional views ofA the transducer of Figs.1 and 2 taken along the lines 4.,-41 and 4A-4A of'Fig. 2;

Fig. 5 is a partial top View of the transducer drive` withy the top ofthe housing removed and the turntable partially shown in section;

Fig- 6 is a plan view of a record member suitable for use withthetransducer of the invention;

Fig; '7. is a schematic showing of. one form of transducer drivecontrol;

Fig. 8V is a schematic showing of a transducing circuitwith which theapparatus may be operated.; and

Fig. SiV is a schematic showing of a simplified tranSducing circuit.

Fig- 10;- is, a view similar to Fig. 1- showing a further form oftransducer apparatus of the invention; and

Fig; 1l is a sectional view of the apparatus of Fig. lo taken along lineII--l i.

Fig. 1 illustrates one practical form of magnetic record transducingsystem embodying the invention. This transducer includes a rotatablymounted record member holder in the. form of a` tableY I--Zii having acentral bearing support I.22 heldy in place in a generally box-likehousing [-24. As shown, the bearing'support i-22 ishleld in a bearingvsocket I-26 having a collar I-,2V and clamped to ther upper surface l-SBof the housing by the spring friction grips i-32. The bearing supportl-22 is shown as including a lower cylindrical extension -34 iittingwithin the socket I-26: and held against, removal by a spring retainerengaging in a slot lf-SS,

The rotatably mounted table l-20, which is,

quite similar to the conventional phonograph turntable, mayhave adepending rim I--d for engagement and operation by driving means shownin the form of an A. C. induction motor, i-42. The rim drive isestablished through the step-down friction drive includingl the` rolleri-lic held on a slidable shaft i-fi together with the rim` engagingroller l-Q and directly driven. by the motor shaft I- against which itis held in contact as by suitablebias means such as. a spring l-fil. Thepassageway I-5 in the housing cover 6 3@ receives the slidabledriveshaft i-e. The rollers |44 and Hi3-areprovided with resilient sleeves ortires UMr and I43Atosmoothly supply power and prevent thev transmissionvof vibrations through the driveto the` turntable.

Pivotally mounted on the upper-surface of= the housing beside theturntable indicated at l-SZ there is shown a transducing arm l--54 whichholds a magnetic transducing head I-56. The arm I-li is shown in theshape of an inverted channel having an upper Wall I-58 the. ends ofwhich are bent downwardly to. provide side walls l-. The arm 1.--54L isloosely. held, pivoted around a horizontal axis by openings I-62 in theside walls l-Bll which. t over and are engaged by the ends of agenerally U-shaped clip l-B4 which are bent over to form. generallyhorizontal detents i-SS projecting through the openings I--62. The clip#-641 is in turn pivotally held to the top of the housing so as to berotatable around av vertical axis'.

The transducing head lincludes pole pieces i-e, shown as formed magneticsheet material aligned and shaped so that their lower edges formsmoothly rounded pole faces l--l separated by a small non-magnetic gapl-1I. Windings |--l2` surrounding the pole pieces are connected to the`transducing amplifiers which may be contained within the housing I--Mvby means.v of the shielded cable I-'l4 fitted within the channel of armi5i and passing through the bottom of the clip` l--lij and through thetop of the housing l-3.0.

The transducing arm l-54 whichv in plan View is curved, as indicated inFig. 1, has aiiixed thereto in its intermediate portion a guide. pin|-14 rotatably mounted in a pin socket [-18 which isI anchored to theupper wall lof the arm. The upper end of the guide pin lprojects abovethe armand is enlarged to form al manually rotatable head I.-8,` and thepin is held 3 in place by a, split spring ring [-82 fitted in aperipheral slot [-84 in the body portion of the guide pin [-76.

The arm openings [-62 are shaped to loosely receive the clip detents[-66 thereby permitting some turning of the transducing arm [-54 aroundits longitudinal axis with respect to the housing and turntable inaddition to the tilting of the arm [-54 around the horizontal axisdefined by the detents.

The arm also holds switch means shown as micro-switch [-36 suitably heldand having a vertically movable sensing member [-88 projecting below thearm, as shown.

The turntable [-2 which may be covered with a layer of flock [-2[ in amanner similar to conventional phonograph tables has a short aligningpin [-89 projecting upwardly and fixedly held intermediate its centerand outer edge. A guide disc sheet-like body portion [-92 and acentrally raised grip boss [-94 has a central mounting socket [-96 andan aligning recess [-98 by means of which it may be centrally fittedover the turnable on the upwardly projecting end of the bearing support[-22 and held in xed relation to the turntable by the aligning pin [-89.The upper surface of the aligning disc is shaped to form a guide groove[-99 which may be in the form of a generally continuous spiral for -1[-90 having a circular a central opening [-33 and an aligning openrecordmember [-3[ and mounting and align- :l:

ing it as shown. The arm [-54 is then manually placed in a position suchthat the pole faces [-16 of the magnetic head [-55 contact the uppersurface of the record member while the lower end of the guide pin [-16engages and nts in a portion of the guide groove [-99. Actuation of therim drive will then cause the turntable to rotate and carry with it therecord member [-3[ and guide disc [-90 while the guide pin [-76 causesthe transducing arm [-54 to be fed in a generally radial direction withrespect to the turntable, pivoting around a vertical axis at [-52. Theguide groove [-99 may be so arranged that the feeding movement of thearm is outwardly from the center of the guide disc so that the polefaces of the magnetic core [-55 scan the upper surface of the recordmember I-3I along a generally spiral scanning track.

To ensure the proper aligning of the scanning trace of the record memberwith the actual position of a recording thereon, the guide pin [-16 mayhave its lowermost point eccentrically positioned so that manualrotation of the head [-853 can be used to adjust the position of thepole faces with respect to the guide groove [-99 and also with respectto the surface of the record member [-3I.

The switch [-86 is shown as so mounted that its sensing element [-88,which is downwardly biased, is held up in the switch closing positionshown in Fig. 2 during transducing operation by the upper surface of theguide disc [-90. However, when the transducing is completed and thetransducing arm [-54 is in its outermost position, the sensing member ismoved far enough so that it projects beyond the outer edge of the guidedisc so that the sensing element [-88 is free to move downwardly andopen the switch. The switch may be connected to stop the rim drive as byopening the supply circuit to the driving motor [-42.

Manually operable means may also be provided for interrupting the rimdrive when desired'. As shown, this control may be in the form of a knob[-91 rotatably mounted on a shaft [-95 pivotally held on the upper wall[-30 of the housing and having a ange [-93 connected as by link [-9I tothe slidable holder of the movable shaft [-45. An arm rest shown in theform of a clip [-81 is mounted to receive and grippingly engage a sidewall [-56 of the tone arm when retracted into the position shown in thedot-dash lines in Fig, 1.

The knob [-91 may be operated to interrupt the turntable drive when theapparatus is in use by rotating the knob far enough to cause the link[-91 to lpull the slide plate holding the slidable shaft [-45 awayagainst the action of the bias [-47 so that the roller [-48 isdisengaged from contact with the rim [-40. The small amount ofresistance to which the turntable is subjected by contact with the guidepin and transducing core [-56 of the arm [-54 is suicient to immediatelystop the turntable when the driving contact is broken. The rollers I-Mand [-48 may be kept in rotatory motion during the interruption of theturntable drive by maintaining the driven engagement of the roller [-44with the motor drive shaft [-46 under the biasing inuence of the spring[-41 in spite of the sliding of the rollers toward the knob [-91 andaway from driving engagement with the rim [-40. Such maintenance ofmotion enables prompt acceleration of the turntable to proper operatingspeed when the transducing operation is continued after an interruptioninasmuch as the rotational inertia of the idling rollers will not add tothe rotational inertia of the turntable.

A simple interruption of the power supply for motor [-42 may also beused for interrupting transducings without materially lengthening theduration of the turntable deceleration and acceleration periods.

Transducing operation are initiated by mounting the record member [-3[in place, as indicated above, and then lifting and carrying the free endof the transducer arm [-54 inwardly towards the center of the turntableuntil it engages the knob [-94 of the guide disc and further inwardmotion is prevented. This knob [-94 is so shaped that it acts as a stopfor the transducing arm and automatically determines the portion of therecord member engaged by the pole faces [-10 of the transducing core forthe commencement of the transducing operation. After bringing thetransducing arm over as far as the knob will permit, the free end of thearm is lowered to bring the pole faces into engagement with the recordmember, The loose pivoting of the transducing arm at the clipautomatically permits the arm to longitudinally tilt and adjust itselfso that the lowerend of the guide pin [-75 also rests against the uppersurface of the guide disc [-90. The weight of the transducing arm andits attached openings is so distributed and the loosely held pivotalconnection at the clip detents [-62 is so adjusted that the lower end ofthe pin is held against the upper surface of the guide disc by a Voflimit switch l-5.. 'is of the single-pole double-throw type, one contactI-l'l being connected to the supply, such ,used on phono-graphs..

force vsuflicientl toassure the proper guiding of the-pin alongr` thespiral guide channel |e-.99, wh-ilea-t the same time the pole faces ofthe transducing core I-55 areheld against the` record member by a smallforce, of the order of several grams, suicient to establishl effectivemagnetic inter-linkage with the record track. Additionally, theyieldfable layer I-Zl together with the loose pivoting of the transducerarm are arranged to permit a yieldable flexing of the record member l-v3Il where it is engaged by the pole facesv 1.-10 by the small contactingyforce so. that. the convex pole faces are engaged along an elongatedportion witha record track. This yieldable contact feature assurespositive interlinkage with the diminutive non-magnetic gap ofthe polefaces. in spite of' ini-nor variations: in the exact positioning ofthisv gap. with` respect tothe record track, as more fully explained inthe Begun application, Serial 612,728, filed August 27., 1945, and asclaimed therein.

At. the same time, as the transducing arm is lowered into. operati-ngcontact at. the initiation of a transducng operation, the sensing membert--ii'of limit switch |.-3. is inwardly actuated by contact with theupper surface of the guide disc and may be connected in the drivingmotor supply line to automatically energize the driving motor and beginthe transducing. Rotation of the turntable andi guide disccauses theguide pin i l-l tofollow the guide channel [-99, thereby causing thepole faces i-l to trace a spiral path over the record member I-3l. Theswitch t-- is so arranged that. when the transducing operation is aboutfinished, sensing member I-88 I carried outwardly by the transducing armis brought beyond the edge of the guide disc l-SD permitting the.downwardly biased sensing member to move downwardly opening theenergizing circuit of the drive motor I-fl2 and promptly stopping thetransducing..

Fig. 7 shows one arrangement for operation The switch as here shown asthe conventional alternating current power line, to directly energizethe motor I42 through the switchl blad@ l--l5, the circuit beingcompleted through the other connector shown. A

. rectifier l-f s, such as thesmall selenium rectifier, Ais connectedbetween the contact l-Tl and the blade i-l5 for supplying D. C. to themotor when the switch blade !-'-?5 is withdrawn from engagement withcontact l-H. A filter, such as the capacitor I-'l' is connected to theother contact l-l of the switch so that engagement vof the blade in itsdownward position with the contact I-l effects ltering of the rectifiedoutput of rectifier l-&9. The switch I-86'may be .of the snap typerequiring very little force for actuation from one position to the otherand commercially known as micro-switch. During transducing the switchblade I- is held against its upper Contact i-ll to supply the energizingcurrent for the motor |42 which may be of the conventional A. C.induction type ordinarily The completion of the recording frees theupwardly held switch blade I-'i so that it snaps downwardly engaging itslower contact i-l3, thereby completing a circuit for establishing afiltered D. C. feed to windings of the drive motor. As explained andclaimed in the co-pendng Dank application, Serial No.

696,878, filed August 16, 19,46, the passage of D. C. through thewindings of such-a motor establishes "f 6 a. brakingy action which`rapidly dleceleratesy the motor shaft and' quickly brings-.itto a halt.

Fig. 81 shows the generali relationship. of Que practical form of amagnetic record transducing' apparatus and its circuit elernentsAutilizing; a single magnetic head for recording, playback and erasingundesired portions of recorded matter along selected parts of recordtraces by means of the sam@y oscillator which supplies. the high fre:-quency bias during the recording process, and utiliz-ing one of theamplifying stages of the play-.- back or recording amplifier circuit foramplifying thel oscillations of the bias supply source in order toenable the amplified high frequency currents` of the'` bias source toeffect the desired erasure of signals magnetically recorded along therecord trace.

The magnetic record reproducing device shown diagrammatically in Fig. 8comprises a magnetic head l-56, such as described above, arranged torecord signals along a magnetic record trace of a moving magnetic recordsheet member i-Sll a single sound transducer device l-IZ serving both asa microphone during the recording process and' as a sound reproducer orloudspeaker device during the playblack process; a control switch 'I-I5for selectively establishing playback and recording circuit conditions;andv a circuit network generally designated 7-23, including the elementsof the amplifier bias supply source and the electric power supply forthe amplier and' bias supply source.

The sound transducer 1--I2 is of a conventionally known type Vwhichperforms the function of a microphone in converting sound signalsreaching it into corresponding electric signals, and as a soundreproducer in converting electric signals supplied thereto into sound.Either a piezo-electric crystal sound transducer or a voice coil typeelectro-magnetic sound transducer may be used.

The circuit network 1 -2d has three amplier stages associated with thevacuum tube amplifier elements 'l-2I, '1-22, 1-23 and a bias oscillator4stage associated with amplier vacuum tube element 'l-2L The amplifierstages of the tubes 'L -2l, '1 -22 and l-Zd are arranged to operate incascade as a three stage amplifier during the playback process, theseveral amplifier stages being arranged to be resistance coupled to eachother. During the recording process only two of the amplifier stagesassociated with the tube elements '1 -22,1-23 are utilized to amplifythe signals supplied by the sound transducer 1 !2 operating as amicrophone and delivering the required recording currents to thewindings of the magnetic head 4Q. During the recording process themagnetic head is also supplied with the required high frequencyoscillatory bias currents produced by the oscillator stage associatedwith the tube element 'l-Zfi, the electrodes of which interconnect withthe circuit elements shown and selected so as to generate high frequencyoscillations of the order of about 30 k. c., for instance. The electricoperating energy is supplied to the amplifier stages and the oscillatorstage by a power supply source shown as a twophase rectifier tube -3!through a conventionally connected transformer to a domestic currentsupply source, for instance, of v. A. C., the rectifier alternatingcurrent being provided with a filter network 'EL-32 delivering highlyltered D. C. at terminal 'l-33, and less filtered D. C. atv terminal '1-34,. To the which is supplied highly filtered D. C. B+ supply filterterminal 1-33 lare connected the plate circuits of the initial amplifierstages of tube elements i-ZI, 1-22. To the less liltered D. C. B+ supplylter terminal 7 34 are connected the plate circuits of the outputamplier stage of tube element '1 23 and of the oscillator stage tubeelement 1 24. The lter circuit includes also additional resistanceelement 1--35 to provide the required operating bias for the input gridof the amplifier tube elements 1-22, 'I+-23, L -24.

The record-playback switch 1-l5 is shown as being of the conventionaltype and its contact blades may be actuated either to the playbackposition, in which it is shown, or to the opposite recording position.There is also shown an additional multi-blade contact switch i-li-Swhich may be of the type whichkeeps its contact blades normally biasedto the position shown, the

blades being brought to the opposite operative position only whensuitably actuated as by pressing a pushbutton indicated at 'l-M.

Further features of the magnetic recording device shown diagrammaticallyin Fig. 8 will appear from the following description of its operation.

It is assumed that the erase switch T ll remains in the non-operativeposition shown, in which position its contacts bridge over completebridging or jumper connections between the circuit portions indicated bythe U-shaped dash line jumper connections designated i-fiz.

With the record-playback switch 'i-i in the playback position shown itsfourth movable conn tactor elements establish the following circuitconnections 'which provide for the playback of magnetically recordedsignals. The ungrounded lead from the windings of the magnetic head l-Seis connected through the irst contact member of the switch to the inputlead 1-35 of tube element 'fi-2i of the iirst amplifier stage. Thesignal input supplied by the magnetic head is amplied by the threecascade connected amplier stages of tube units '1 -2l, 1-22, and !--23,the amplified output being supplied by way of output lead 'i-Si of tubeunit 'i-23, and the second contactor of the selector switch 'i i5 to thesound transducer device -I2, which delivers sound output correspondingto the electric signals impressed thereon, the circuit connection beingshown. rlfhe playback operation proceeds as long as the recording mediumi-3i moves relatively to the head 4 55 while the selector control switchi-l remains in playback position. Throughout such playback operation theoscillator associated with the tube unit 1 24 remains de-energized.

When the selector switch l-l is operated to the opposite recordingposition its contact blades establish the following circuit connections.In the recording position the sound transducer device '-I2, which nonroperates as a microphone, is connected through the second contact bladeof the selector switch -l to the input lead 7-31 connected to the inputgrid ofthe second amplifier stage of tube unit 'E-ZZ-which operatesduring the recording operation as the iirst amplier stage, and theoutput of which, after amplication by the output amplier tube completedby the ground connections D unit '5 2 is impressed through the outputlead 8, the ground connections shown so as to impress upon the windingsof the record transducing head 40 currents which produce in theeffective gap region of the head the desired magnetic recording ux.

In the right-hand position of the selector switch "1 -l5 its fourthcontact blade connects the B+ supply terminal 7 34 to the plate circuitof the oscillator tube 'l--24 and causes it to produce and deliver therequired high frequency bias oscillations. The oscillating circuits ofthe bias oscillator tube unit '1 -3 4 have an output lead 1-31.including a condenser 'i-38, through which the proper component of highfrequency biasing current is supplied by way of its connection to thethird contact blade of the selector switch to the windings of thetransducer head [-56 so as to produce in the effective magnetic gapregion of the head the proper component of high frequency alternatingbiasing flux. The coupling condenser '1 -33 in the oscillator outputlead and the other circuit elements of the system are so designed as tomake a suitable component of the high frequency oscillations produced bythe oscillator tube unit '1 24 with the amplified signal currentsupplied by` the microphone transducer 'l-IZ in such manner as to inducein the eiective gap region of the recording head l-56 the desiredcombination of the signal recording flux and the superimposed highfrequency biasing luX component. It will be noted that with the circuitarrangement shown the output lead 7 31 of the single oscillator stageremains connected to the windings of the recording playback head 4U notonly during a recording operation but also during the playbackoperation. As shown, an additional condenser 1 39 is connected acrossthe B+ supply lead connection to the plate circuit of the oscillatortube unit 'l-24, this condenser 7-39 serving as a capacitive energystoring device which, in conjunction with the other elements of theoscillator circuit, operates to impress upon the windings of themagnetic transducer head 3-45 a decaying high frequency oscillatingcurrent of such character as to automatically eect a neutralization ofthe magnetic core of the transducer head Whenever a recording operationis stopped, either by the fle-energizetion of the recording circuits orby actuation of the selector switch '1 15 from the righthand recordingposition to the lefthand playback position.

With such arrangement the oscillator associated with the tube unit '1-2li continues to produce high frequency oscillating current andcontinues to supply them to the windings of the magnetic head lill afterthe plate circuit of the tube has been disconnected from the B+ supplylead, the oscillating current so supplied to the head decaying within afew oscillating cycles and thereby neutralizing the magnetic core of thehead. With the arrangement shown the oscillator stage associated withthe oscillator tube unit 'l-2 is loaded during a recording operationboth by the windings of the magnetic head 4 5'5 as well as by thecircuit elements of the amplifier output stage of tube unit I+-23 towhich it is connected by the third contact blade of the selector switch'1 -l5, and the oscillator circuit is so adjusted as to provide anoscillating output of the proper biasing level when the oscillator stageis subjected to such compound loading.

The circuit elements of the system may be readily so designed that whenthe selector switch 'I+-l5 is moved from the recording position to 'theyplay position, the oscillator 'outputflead 1 -"31 is 'disconnected fromthe amplifier output Vlead 1-36, therebyfdecreasing the oscillator loadand causing the oscillator :output "to Vincrease or surge Aup"fromtheibias level to a level high-enough for 'supplying tothe windingsdf themagnetic 'head I-SS oscillating current suiiicient to saturate'the magnetic core ci the head "and'bring about its magneticneutralization by 1a succession of decaying oscillating cycles.

To secure effective erasing 'action under such operating conditions,theelernents of the selector switch '-'i-I 5 maybe so adjusted that`when actufated `from the record to the 4playback position its thirdcontact'blade operates iirs't to open the connection of the oscillatoroutput lead from the ramp'liiier output lead before the fourth contactAiirst magnetizing cycle of 'which is below the "level required forsaturating 'the magnetic core lof the head. In other words, theinitialor`highest level ofthe 'demagnetizing current that has 'to be supplied`,by the bias oscillator stage `to the magnetic head vat the Tend of arecording cycle need not be ihigh enough to completely saturate themagnetic "core, tand the surge level of the highly saturated load outputneed y.not be very much higher than Athe bias Alevelin order lto secureveiiective demagnetization of Vthe head ,at `the rend 5' of a recordingoperation.

Withoutlimiting the scope o the invention, but in order to enable readypractice of the `invention, there are given rbelow data of -one form ofmagneticrecording.device lof .the type shown inFigqS which is now-on.the .market and serves Ias a low costspeech dictating device.

The magnetic head vI.5 is-of the type shown inthe Begun application,Serial No. 4,688,738, filed August 6, 1946, .which .issued as Patent No.2,513,617 on July, '4, 1950 .or Korneiapplication .Serial No. 688,034,filed .August 2, 1946, which issued as Patent JNO. l2,523,576 :onSeptember 26, 1950.k The .two VVtube `units 'l-2/l, 1h22 form parts of a.single ltube .type SSL'l-GT. The tube units "l'-"3, l-ZE form .part :ofra single tube GSNLGT. Rectifier tube J-Si is :a type 6X6- GT/G tube.The ,plate-circuitof the oscillator tube .unit 'l---iki includesraareactanceof 3() millihenries. The magnetic -reccrd .transducingdevice shown .is ,being sold A'on the market under the .trade AnameMail-A-Voice.

vIn 'accordance with the invention, a generally simple .magneticrecord-:transducing Adevice of vthe type described above lis combinedwith a simple .erasure control farrangementwhichfma-kes vit -possible toutilize the single head l-4':6, which lis .used lfor i carrying fon,playing fback and recording operations with-at-highfrequency-oscillating current of a greater level than normally suppliedby the oscillator -in order to make it `possible .to `erase a selectedportion of :la `record made bythe recording head white the sequence'convtrol switch 'l--i .is either Ain 'the recording operation or invthe playback operation. In `the arrangement of 1iig, 8 4the addi-tionalerase .control switch l4iis=provided-to selectivelyiniterrupt eitheraplayback ora recording operation .and establish -circuit nconnections.by `means of which the oscillator stage is maintained in an,

`oscillating condition, .-and'itsoscillating output is impressed on one"or more 'amplifying stages of the :amplifier in such manner vas tolsupplyam'pliiie'd high 'frequency -roscillation tothe windings `of therecording head sufficient for producing in 'the feective 'gap region fofr.the .magnetic core of the head a .high Ifrequency erasingiiuxrequire'dt-for erasing records made by Aor lduring :a previousrecording operation. As stated before, the erasing rswitch 'l-'ll may beof the type s'hown and its blades maybe permanentlybiasedto establishthe y'bridging `connection shown which make it possible to carry onk"either "playback `operation lor recording operation under the control`of the selector `switch "1 15. The 'erasing switch 1!-40 iis, however,effective itc at yany "time interrupt r a recording operation Aand toestablish the follow- :ing erasing rcircuit connections to'the headwh'enits contact blades Jare actuated to :a fright-hand operative positionasseenrin Fig. '7. #In the .right- -hand operating :position ftheerasingswitch -l wiil :establish 'following operating condition. Its fth'right-'hand `contact -blade `|in "the righthand position connects theplate circuit "of the oscillator tube Aunit l'1 -24 'to `,the B+terrninal i1-34, fthereby energizing the .'oscillatorstage fand fcausingit to vgenerate the thigh'requency oscilla- JYtions. The `third andfourth right-'hand Acontact lades of lswitch1-401inthefright-handposition fconnects the output lead '1 -31 fof thesingle oscillator stage tube unit 1 -124 to i'the inputLlead'l-ll of thelast amplier stage of tube unit 'l-212 and disconnects them from `their'normal `'circuit lconnections inorder to impress Aon the output `lead'l-of the amplierfnutput `stagr-:farnpliedhigh frequency oscillatingcurrent .of 7the magnitude required for producing 'with the :magnetichead :I- the -desired erasing flux.

The output lead 1-'36 fof fthe outputamplier tube 1 23 is vconnected `bythe first -and second contact blades "of fthe erasing switch V'l---Ml intheir right-hand position to =the windings `Vof vthe `4,recordtransducing :head -I-J56 for lsupplying fit with the .ampli'ed highfrequency `oscillations 'of a level .sumcient Vto produce in :its`effective vgap region the required :erasing `flux. |Ihe erasing switchl-d maybe conveniently mounted on one ofthe readily accessible :wallsofthe recording device so that :any time `during a recording operation-or playback operation va desired portion of a recorded record trace`may bbe erased by mo- V`mentarily v`actuating the erasing switch "l--Mlfrom vthe release position to -anoperative right- -hand position shown.IAlthough Vthe erasing rswitch L-AU vshown is indicated as one which ismanually operated, it may obviously be remotely controlled asby=cornbiningrit with-arelayor solenoid which is arranged vto operateits `contacts from one position to another.

When signals are Vmagnetically recorded Aon .narrow adjacentlongitudinal traces `of a continuous magnetic recordsur'faca isuch asasheet member 3| described above, diculties are `encountered in playingfback the magnetically recorded signals because the Vmagneticwave .ele-

" 'ments formed by the recorded signals along the adjacent Vrecordtraces of the recording fsurface produce spreading magnetic leakage eldslwhich are picked up `by the 'record 'transducer head i62 whenplayingback therecording signals. In `the recording"arrangement'shown,the cross-talk difficulties encountered 'in playing back magneticrecords -from adjacent 4narrow record traces Y`of a Amagneticirecordsurface are overcome -by using vas a recording medium a :magneticmaterial fexlllbting 2l high coercive force of the order of 100 oerstedsor more, and operating the recording medium at a low speed of the orderof about 4 to 8 inches per second so that the signals of the lowestrecorded frequency are recorded in the form of suiiiciently short recordsignal waves as to reduce the spreading leakage iield below a disturbinglevel in the manner disclosed and claimed in the copending application,Serial No. 612,728, led August 27, 1945, by S. J. Begun.

Fig. 9 shows a modication of the transducing arrangement for use withthe apparatus of Figs. 1 through 7. In this form the general transducingfeatures are quite similar to those of Fig. 8 and similar parts arecorrespondingly numbered.

As shown, the transducing control switch S-I is set for a playbackoperation and the On-Oif switch 8 1!! is closed, supplying power to theturntable motor 8 59 and to the amplifying tubes 8 29 and 3 39 throughthe rectier 8 3l. Signals picked up by the magnetic head 49 are appiedto the grid of the first amplifying stage 8 2! without requiring aseparate grid return circuit such as is commonly offered by a grid leakresistor.

The signal is amplied, fed through the second and third amplifyingstages 8 22 and 8-23 through the volume control potentiometer 3 5() andthence to the acoustic transducer 8 I2 through a pair of the contacts ofthe iack 8 92 and the plug 8 54. The second amplifving stage 8 22 isoperated without bias and the third stage 8 23 has a bias supplied bythe cathode resistor 8 43 so that the ilter network 8 32 is simplied.

The potentiometer 8 6!! and the switch 8 Iil may be mounted foroperation by a common control as shown.

For recording, the switch 8 5 5 is set to the extreme right-handposition in which signals from the acoustic transducer 8 I2 are fed tothe input of the second amplifving stage 8 22, thence through the thirdamplifying stage 8-23 to the magnetic read 40, where a bias is suppliedfrom the output of oscil'ator 8 24 by wav of capacitor 8 44. At the sametime tbe first amplifying stage which is not used for recording has itsgrid grounded to decrease the noise level.

The acoustic transducer 8 l2 may be of the type suitable for bothchanging sound signal to electrical currents and for reproducing thesound signals from electric currents, as indicated above, and may beprovided with a convenient hand switch 8 65 by which the turntable maybe operated. As shown, the energization of the turntable motor 8 5!) maybe provided through either the switch 8 65 of the remote control type,switch 8 58 which may be mounted directlv on the instrument housing, orjack 8 19 in which a foot switch may be plugged. Solenoid 8 '52 andresistor 8-14 are kent in the turntable motor circuit. Solenoid 8-72 inseries with the rectifier 8 16 is arranged for disconnecting theturntable motor drive as by pulling the idler rollers l 4| and I-43 ofFigs. 2 and 5 away from the drive position shown. In this mannerwhenever a turntable switch is onen to stop the turntable motor drivethe solenoid 8 '52 automatically disconnects the engagement between theturntable motor and the turntable. The armature of the solenoid 8 12 mayalso be provided with an extension in the form of a brake for engagingthe turntable rim and applying braking forces whenever the solenoid isactuated so that the stopping of the turntable .is practicallyinstantaneous. The windings of the solenod 8 12 may be shunted by acapacitor, as

shown, for nltering the A. C. ripple from the D. C. passed by therectier 8 16, thereby eliminating chatter in the solenoid armature.

The resistor 8 74 functions to admit a small amount of energizingcurrent to the turntable motor 8 59 so that its rotor is not completelystopped when one of its control switches is open. The resistor 8 '14 isadjusted to admit a small amount of current sufficient to keep theturntable motor running at somewhat reduced speed so that the inertiarequired for restarting it is considerably decreased.

In the above arrangement any of the switches 8 i35 and 9 558, as well asthe switch inserted in the circuit of plug 8 19, will operate to shuntthe resistor 8 14 and the solenoid 8 2, permitting full current supplyto the turntable motor 8 58 and de-activating the solenoid` so that theturntable start is substantially instantaneous.

The jack 8 89 may be used for supplying power to accessory equipment,such as loudspeakers, which may be operated in conjunction with theapparatus.

A feature of this equipment of the invention is the simplified erasingcontrol. An erase switch 8 82, which may be of the simple hold-down typebiased to outward position in which it establishes a B+ power supply .tothe third ampliner stage 8 23 by means of the lead 8 84, as shown infull lines in Fig. 9. In downwardly held position, as shown in dashlines at 8 83, the erase switch establishes a B+ supply to theoscillatcr 8 24 through the connector 8 88. The erasing connection 8 83,8 89 is shown as shunting a B+ supply to the oscillator normallyestablished through one of the contacts of the transducing controlswitch 8 I5 when set in record position.

With the amplifying circuit values as given above in connection withFig. 8, the oscillator 8 24 and the iinal amplifying stage 8 23 are soarranged that with the apparatus set in recording position the outputsof the amplifier 8- 23 and the amplier 8 24 are both connected to thewindings of the transducer head 49 and the amp-liner output constitutesan appreciable load on the oscillator output. The oscillator 8 24 whichis normally capable of producing relatively large amounts of highfrequency energy is so loaded by the amplifier 8 23 during a recordingoperation that its output is greatly diminished and becomes of theproper magnitude for biasing the recording currents passing through thewindings of the transducer head. With the switch 8 I5 in the playbackposition, however, only the input of the rst amplifier 8 2! is connectedto the transducer windings, together with the oscillator output.Inasmuch as the input of amplifier 8-2l is of extremely high resistanceit does not appreciably load the oscillator 8 213 so that actuation ofthe oscillator causes the generation of high frequency currents largeenough to demagnetize the portion of the recording medium linked withthe magnetic core 49.

ln the operation of a transducer with the controls such as shown in Fig.9, erasure of any portion of a recording may be simply accomplished byholding down the erase switch 8 82 to the position shown at 8 83 withthe transducing control switch 8 l5 set to playback. In other words, theapparatus is set for playback and the operator listening to thereproduced signals merely holds the erase switch down when 13 vtheirecording to =be erased Ais reached and 'keeps it :down :until all :of-the undesired `signals have rbee'n removed.

The.eraseswitch18'%2 may be mountedl on the topof the transducer housing-I30, asshcwn in :Figs r`1 and 2 kfor example, or'may beef the remotecontrol type .making connection lwith the 4amplifier through the -jack8-64 tand the plug 8-62.

:The jack `8-.10 may be modified if desired to include a third fcontactfor operating :a ybackfstepping arrangement such vasthe one shown inzthe copending aVi/'illiams application, Seri-al No. 651,637, .f'ledMarch 2, 1946, now abandoned.

.@ne or more yfoot switches may -be arranged to be plugged finto thejack -8'|0 -to-either operate the transducerdriveor theback-stepasdesired. fEor --close range lwork Where no remote Vcontrolconnection is needed `and lone-of the operators Ahands is free, fthetransducer may be back-- fsteppedbymerely lifting the-transducer arm andmoving kit back :to where its guide pin enga-ges the `previously passedgroove on zthe vguide dise, after which yitcan-be lowered. Thisoperation ais Nery isimple -to fperform .since .the guide `pin may `-bemade .to click over fthe Yridges between the fgrooves, andthe operatorcan easily keep track .ofthe numberof clicks. The iback-step mayac-.cord-ingly be a jumpof-.one-:or Ymore grooves Aper- .formed -in .asingle operation.

The :magnetic recorder of the type disclosed be utilized -to keep therecorded :magnet Waves short enough in length to suppress cross-talk asdisclosed and .claimed :in the (1o-,pending :Begun .application SerialNo. 742,793, iiledApril v21, 19437 as a continuation-'impart 4ofapplication lSerial No. 540,667, -led'June 16, 11944, now Patent No.2,419,195 granted April 22, 1947.

The record member -l-'Bvl lmaybe 'of anycom position. Itrnay,-for'example be a thin-sheet of paper with a permanently .magnetizable`coating applied -to its surface 4and covering the Iarea'scannedbythetransducingpole faces. fAs shown 1in fFig. 6, -thedashlines 1m29 indicate the spiral track along 4which the -transducing4takes place. The'central portionof therecord member is-.cov- 'ered `bythe-guidediscrand is not scanned but it is simpler to extendthemagnetizable'coatinguni- :formlyfacrosstheentiresurface -In onepractical form "the :record'member is a .sheet of kraft paper .9 inchesin diameter and :about v2 mils thick, the coating being a :bondedstratum of permanentl;7 magnetiaable iron `pride lpowder as described inthe co-pending -Kornei 4:applicationSerial No.2685,)92, `iiled July 20,'1946, and .in lthe copen`ding Foley application Serial 4No. 13,092,:iiled August 28, 1945. More than .three minutes or recording can :bemade -on the ,peripheral -twodnch margin of one :surface -of such arecord member with the recordrotated-.at

20 revolutions per minute. I

'Ihe ,paper record .may :be iolded, acreased Since the `cross-tall:`effect is CII crumpled and even -torn `Without destroying `therecording which may be'reproduced Aby smoothing the record member,mounting it on vthe turntable 'and operating the transducer with theswitch yset -ior playback. Any torn Yor severed portions 4of the recordmay be held inplace as'by'anadnesive Vtap'e'secured-to the-backfsurfaceof the record-on -bothsides of thetear.

The record member may also be made of a-relaytively stiff material suchvas metal, brass, forexlample, with a permanently magnetizable `coating4deposited on one surface. The-electrolyticcoat- :ing'of mixed cobaltand nickel, as descrbedfand :claimed in the ctx-pending Zapponiapplication :Serial No. 738,973,1ledApril 2, y1947, also makes anexcellent magnetic record 'Stratum having fa coercive iiorceof '2()0` ormore oersted-s.

Other record materials, such 'as homogeneous :permanently magnetizablemetal, Ylike stainless steel or non-magnetic rmedia, having 'aninterspersed rpowdered permanently magnetizable composition `lilre thehigh coercive force `iron 1a1- Nloys, may also be used.

The thickness ofthe 4record Imembers `'has `no -eiiectzon :thetransducing. Both surfaces ofthe :record may be-coated withthepermanently niag- .netirable strata so that more of the available,record vsurface :is utilized, cross-talk between the two surfacesrbeing prevented on Ythe very thin `sheets :in the :'s-ame mannerindicated above Yinthe ce-.pending Begun applications for the 'adjacentturns of la :single surface. Thin 'record members maybe reinforcedadjacent 'the aligning'elernen'ts if-desired.

'According to fa modiiication 4of the invention, the transducer may fbeAarranged vWith a record support separate Vfrom the Aguide disc support.In this manner the record fmemher be held for transducing `ata Zlevelspaced "from the levl at which lthe vguide ydisc is held. rllie'recordsup- V:port may be so located vthat the yrecord 'can be vnriountedlfor-transducing, or removed'a'iter transducing Without requiringmanipulation of the guide disc, :and more of the record Vsurface can `bef-utilized. The transducing armmayhavefan vextension or addition =forengaging 'the guide disc and cooperating with it in the 'manner :shownabove for initiating 'and/or terminating atran's- -ducing sequence. .Theguide discmay -alsobe held ein `inverted Vposition with respect to therecord member suitable vlinkage fbeing provided to `hold .a `guidestylusagainst the guide discin one'dire'ction iWhile `the transducer'core is held against the :record in the opposite ydirection and 'tocause "si- .lmultaneous Yi-*etra-ctionof 'both the stylus 'and thetransducing arm.

According to another modification oi the linrention the `record supportand the guide Adisc support may `be ktilted Awith respect 'to thezhoritzontaland may also be 'vertically positioned. A separate :supportccnstruction -in which the sup- :ports are #positionedvertically-*crateri angle Apro-- vvides a compact arrangement venablingsimpler Yguide disc vmanipulation :in that fobservation oi themanipulation ispossible so that'it is not necesy.sary either :tofspaceythe support-star apart orto .mount vand fdisrnount 'the guide discs"without benefit of vision.

In la v.vertically supported construction ia'coordfingto the inventiona-turntableisimilar Ito that fof l and 2 miay be provided Witha centralpost extending horizontally-out -froin 'both races. 'One 4face receivesthe record member fand .the other inthe guide disc. Theendcr'thepost'on'which @the 75 guide disc .is v.-n'lounted may Ehelprovided with n.

friction catch to securely hold' the disc in place. The other post endis also arranged to securely hold the record member against thesupporting face oi' the turntable as by providing a pivoted extensionwhich can be aligned with the post for 'receiving the aligningaperture'of the record and can be pivoted to a tilted position in whichit resiliently urges the record member against the support.

The transducing arm and guide stylus may be pivotally held from a pointabove the top of the turntable and biased forward each other as by alight spring, to provide the desired firm stable magnetic contactbetween the magnetic core and the record member. For use with limp,pliable record sheets such as those made of thin paper, the transducerarm may also carry a relatively extensive pad member adjacent themagnetic core to hold the thin record sheet rmly against the support inthe region adjacent the points being transduced. The pad member may have.a portion engaging the record member at the uppermost position of itsrotation where the limp record member has the greatest tendency to fallaway from the vertical supporting face. One or more non-central aligningapertures may also be utilized to engage corresponding aligning pins inthe support in the manner shown in connection with Fig. l, to establishanrm driving connection to the record member. The pivotal mounting ofthe stylus and transducer arm may be at places other than above the topof the turntable, suitable counterbalancing being used so that theguidingrforces exerted by the guide stylus yare notrequired to opposeanything but a small fraction of the weight of the pivoted structures.

According to another phase of the invention, the transducer arm may beslidably held on the housing so that the guiding movement of the guidestylus causes the transducer arm to slide with respect to its mountingon the housing Vas well as with respect to the record member. rThe guidestylus of this modification is aligned with the transducer core and theslidable transducer arm mounting. Where the tilted supporting structuremodiiication is combined with the slidable transducer arm, the slidingof the arm should be arranged to be substantially horizontal.

An important feature of the invention is the fact that inexpensive andreadily replaced guide members may be used and the transducing action isautomatically directed to the proper regions without any adjustments ofthe apparatus. The guide members such as guide disc i-Bt may be ofmoldable construction and of plastic composition which cooperates withthe guide stylus in a very effective manner and without generating anyappreciable amount of noise due to friction. This is much superior to ametal-to-metal transducer guiding contact inasmuch as the noise level ofthe metaleto-metal contact is extremely high in the absence of alubricant which would make the use of the apparatus quite messy. In thepractical commercial form of the apparatus, its operation does notinvolve any necessity or opportunity to even soil the iingers of theoperator. The plastic guide discs are readily and inexpensively replacedwhen worn out.

Figures l0 and l1 show one form of magnetic record transducer having asliding transducer head mount as described above. As shown, this formmay have a pair of lugs, 9-29, standing up from the transducer housingand forming a pivotal mounting for the ends 92i of a head mount guide,9-22. The guide, 9-22, may be arranged for slidably holding the headmount, 9-24, shown as a sheet member having an outer dependent iiange,.fl-26, and a pair of inner dependent iianges i-28, all provided withguide apertures, Sl-EEL for receiving the wire shaped arms, S--32, ofthe guide, 9-22. rhe head mount 9-24 is accordingly slidable along thearms, 9.-32, and carries the transducer head, 9-56, as well as a guidestylus, 9-16.

The magnetic head, 9-5, may be held on the dependent flange, 9-26, as bymeans oi the screw, 9-34. The guide stylus may be held on the uppersheet portion of the head mount in a manner similar to that shown inFig. 4.

The head mount 9-24 is also shown as provided with a stop member shownas a protrud ing nose portion, 9-36, which cooperates with a stop limitto determine the starting position of the head mount for beginning atransducing operation. The stop limit may either be the knob, Q-94, ofthe guide disc or a suitably shaped portion, B-ll, of the head slideguide, 9-22.

The other `features of the apparatus oi Figs. 10 and 11 may otherwise begenerally similar to that shown above in connection with Figs. 1 through5. The slidable head form of the invention is used by tilting the headguide, @-22 around its pivotal support, 9-2i, so as to expose the recordreceiving support and prepare it for receiving a record member such asadisc shown in Fig. 6. With the record member in place a guide disc maybe pressed above it in the manner described in connection with Figs. 1through 5, after which the transducer head may be brought into operativeengagement with the starting zone of the record member. This engagementmay be affected by lowering the head mount guide, 9-22, and at the sametime sliding the head mount, 9-24, until its slide limit engages thelimit stop and the pole faces of the head, Q-Si, contact the recorddisc. The guide stylus, 9-55, is simultaneously brought into guideengagement with a guiding region of the track groove of the guide discand the transducing can then be initiated by rotation of the recordmember support.

The transducer head mount 9-24 may also be provided with a switch, 9-86,for automatically ending a transducing operation when the head, 9-56,reaches the end of the'scanning path. The switch, 9-36, may be asensitive microswitch similar to that shown above in Figs. 1 and 2 andmay be mounted on an additional ilange extending downwardly from thesensing element, 9 88, of the limit switch, 9-3S, may be arranged sothat the sliding motion of the head mount along the guide, 9-22, carriesit past the outer end of the guide track disc as the guide stylus, 9-15,reaches the outer-most guide track region. The sensitivity or forcerequired to operate the sensing member, 9-538, is so adjusted withrespect to the weight of the head mount and its slide guide, 9-22, thatthe sensing element is kept in operated condition whenever the headmount is allowed to rest against the guide track disc.

A feature of the form of the invention shown in Figs. l0 and 11 is thatthe pole faces ofthe transducer head are maintained in constant angularrelationship with the scanning path of the record member therebyenabling a more exact and constant longitudinal recording on thepermanently magnetizable portions of the record member.

The head mount-guide such as'the wire carrier 17 9-22 of Fig. 10 mayalso be arranged to hold itself in restricted position for simplifyingrecord changing operations. In the form shown, the lugs 9-22 may haveextensions or pins 9-42 for supporting the carrier 9-22 when it istilted up.

The expression magnetic record transducing" as used herein in thespecication and claims is intended to mean either the operation ofmagnetically recording signals on a magnetic recording medium, or theoperation of reproducing magnetically recorded signals, or the operationof erasing magnetically recorded signals, or any combination of two ormore ofthese operations.

The principles of the invention explained in connection with specicexemplications thereof will suggest to those skilled in the art manyother applications and modications of the same. It is accordinglydesired that the appended claims be construed broadly, and that theyshall not be limited to the specific details shown and described inconnection with exemplications thereof.

I claim:

In a magnetic record transducing apparatus utilizing a record membercomprising a disk of sheet material having an exposed surface on whichmagnetic signals are recorded along a generally spiral physicallyintangible record trace: a base, a rotatable turntable connected to saidbase for supporting and rotating said record member, arm means includingpivot means mounting one end of said arm means on said base for movementof the other end across said turntable, a magnetic transducer headmounted on said other end of said arm for engaging said record member, aguide stylus con- 18 nected to said arm at a location between the pivotend and said other end, a solid circular guide disk of diameter lessthan the diameter of said record member and having a spiral guide groovethereon for engaging and guiding said guide stylus to pivot said armacross said turntable to cause said transducer head to scan said spiralintangible record trace from inside to outside, said guide disk beingpositioned at the center of said turntable and cooperating with saidturntable to hold said record member in iixed position, a circularbarrier structure connected to the center of and extending above saidguide disk for engaging said arm to limit the radially inward pivotmotion of said arm for defining a fixed starting location for said armas it pivots across said turntable from a radially inward to an outwardlocation.

JOHN H. JAMES.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 850,036 Morin Apr. 9, 19071,357,037 Duncan Oct. 26, 1920 1,663,664 Kuchenmeister Mar. 27, 19281,957,158 Crudo May 1, 1934 2,416,135 Appleby Feb. 18, 1947 FOREIGNPATENTS Number Country Date 613,925 Germany May 29, 1935

